Body plans are coordinated to optimize biological function
Review: Animals are mutlticellular, eukaryotic heterotrophs
- Most ingest organic materials
- consume, breakdown internally with enzymes
- Lack structural support from cell walls
- external proteins connect and strengthen cells
- most abundant are collagen (not found in plants/animals)
- Cells organized into tissues
- similar cells acting as a unit
- muscle & nervous tissue allows animals to move
- Body plan = programmed development driven by evolution
Embryonic development key for animal diversity
- Fertilized zygote undergoes cleavage
- mitotic cell divisions without cell growth
- rapid division but overall size stays same
- Early multicellular stage called a blastula (hollow ball)
- protostome or deuterostome = alignment of cells
- Tissue layers develop in next stage (gastrulation)
- develop into adult body parts
- Many animals have larval and adult stage
- larva are sexually immature
- larva look, live and eat differently
Protostomes vs Deuterostomes and the blastopore
- Blastopore: opening of central cavity of an embryo
- In most animals a second opening forms at opposite end
- become openings of digestive tube
- Protostomes: blastopore becomes mouth
- Deuterostomes: blastopore becomes anus
Germ layers (primary cell layers in development)
- Sponges (0), Diploblasts (2), Triploblasts (3)
- germ layers develop into tissues and organs
- Ectoderm:
- Endoderm:
- Mesoderm:
Body Cavities in Triploblasts
- Fluid/air spaces between endoderm and body wall
- digestive track and body wall
- Body cavity called coelom
- cushions organs
- fluid resistance for muscles
- allows organs to move independently
- Not all triploblasts have a coelom
Form and function in biology
Evolution of animal size and shape
- Animal body plans are expressions of the genome, but the product of millions of years of evolution
- Animals body plans are constrained by physical laws
- diffusion, movement, heat exchange
- gravity
- Example: Properties of water and animal shape
- water more dense = surface bumps cause drag
- natural selection favored tapered smooth bodies
- convergent selection across aquatic mammals
Example: Diversity of bird form
Exchange with environment limits animal bodies
- Animals must uptake nutrients, lose waste and exchange gases
- occurs across plasma membrane of cells
- Simple internal body plan: Hydra
- body wall and cavity open to environment
Exchange with environment limits animal bodies
- Animals must uptake nutrients, lose waste and exchange gases
- occurs across plasma membrane of cells
- Body plan optimized for surface area: tapeworms
- thin, flat shape
- lots of outer cells exposed to environment
Exchange with environment limits animal bodies
- Animals must uptake nutrients, lose waste and exchange gases
- occurs across plasma membrane of cells
- Many animals (like humans) have more complex internal bodies
- reduces total # of cells on outer surface
- volume > surface area
- ‘think’ whale versus flea
- Internal structures for exchange evolve…
- highly branched or folded
Exchange with environment limits animal bodies
- Animals must uptake nutrients, lose waste and exchange gases
- occurs across plasma membrane of cells
- Many animals (like humans) have more complex internal bodies
- reduces total # of cells on outer surface
- ‘think’ whale versus flea
- Internal structures for exchange evolve…
- highly branched or folded
- digestion, respiration and circulation
- fluids connect structures to other cells
What are the advantages of a complex body plan?
- External skeleton?
- Sensory organs (eyes, ears, etc.)?
- Internal digestion organs?
- Specialized filtration systems?
- How do internal systems allow life on land?
Hierarchy of animal body plans
- Cells with similar function grouped into tissues
- Different tissues organized into functional units: Organs
- Groups of organs can work together: Organ systems
- There are a limited set of cells and tissues
- epithelial:
- connective:
- muscle:
- nervous:
